110
400 400
.. .....................
30.0 --------- ..... -..-. .. 300 .-.- ..... .- ......... .......... -..-.-.-.
t0
S20.0 ----------------------------- 1- ..- E 320
E 20. -
150 150
0-5 0.7 09 11 1.3 05 0.7 0.9 1.1 1.3
Thermal Diffusivity (ft2fday) Thwnmal Diffusivity (ftlday)
'55 m65 "'V7.5' 5S 'mm,' "7,5'
Figure 5-18 Effect of Thermal Diffusivity on Thermal Gradient
Compressive Strength
In Chapter 4 it was shown that using pozzolans effects short term (15 day)
compressive strength of high temperature cured sampled positively. However, after 28
days, the compressive strength of high temperature cured samples is lower compared to
the room temperature cured samples.
Table 5-11 and Figure 5-19 show the summary of 28-day compressive strength
results for 6"x12" specimens cured in moisture room. The numbers are average of
compressive strength tests for similar mixes. For specimens with 730F a significant
difference in 28-day compressive strength was not resulted. It can also be seen that
replacing a portion of cement with slag helps the 28-day compressive strength of
concrete. The results for high temperature placed concrete showed that replacing cement
with pozzolans (slag or fly ash) reduces the 28-day compressive strength 2 to 3% in the